Scenario: A Citrix Administrator has configured an HTTP load-balancing virtual server with Least Response Time as the load-balancing algorithm. The administrator notices that requests to the virtual server appear to be using the Round Robin load-balancing algorithm. What could be causing the virtual serer to use the Round Robin load-balancing algorithm?

The Least Response Time load-balancing algorithm requires performance data to determine which service is responding the fastest. When a virtual server is newly configured, has just been enabled, or has had no recent traffic, the Citrix ADC lacks the necessary response time metrics. To gather this initial data without delaying client requests, the ADC employs a "startup round robin" mode. It distributes the initial requests sequentially across all bound services. Once it has collected sufficient response time data from each service, it transitions to the configured Least Response Time algorithm for subsequent requests.

A. The Citrix ADC configuration has NOT been saved yet. An unsaved configuration does not affect the currently running configuration. The change would be active immediately upon being applied, regardless of whether it has been saved to the startup configuration file.
C. The services that are bound to the HTTP virtual server are using the PING monitor. The monitor's function is to determine if a service is UP or DOWN. The Least Response Time algorithm measures the actual response time of live traffic, a process independent of the monitor type.
D. Least Response Time CANNOT be used as a load-balancing algorithm on an HTTP virtual server. This is factually incorrect. Least Response Time is a standard, supported, and commonly used load-balancing algorithm for HTTP and HTTPS virtual servers on the Citrix ADC platform.

1. Citrix ADC 13.1 Product Documentation, Load balancing algorithms and methods. In the section "Load balancing algorithms," the documentation states: "For the least connection, least bandwidth, least packets, and least response time methods, the Citrix ADC appliance selects a service on the basis of the service’s current load... To avoid a long wait for a response at the client, the virtual server forwards the initial requests on a round-robin basis. After it forwards a request to each service, it has the load information it needs to begin using the configured load balancing method."

2. Citrix ADC 13.0 Product Documentation, Load balancing basics > Load balancing algorithms and methods. This version contains the same explanation, confirming the "startup round robin" behavior for dynamic load balancing methods like Least Response Time. This behavior ensures the ADC can prime its decision-making engine with real-world data before applying the more complex algorithm.